The utility of microporous solids such as the zeolite-type aluminosilicates, aluminophosphates, and their metal substituted derivatives is well established in industrial processes involving ion-exchange, separation, and catalysis (U.S. Pat. Nos. 4,310,440, 4,440,871, and 4,500,651). The widespread application of these so called zeolitic materials is due to their ability to include molecules and ions in a selective and reversible fashion, a property conferred by the stability and rigidity of their porous frameworks.
Although most of these frameworks are based on the oxide of the metal, a recent invention showed that similar materials can be produced from the sulfide and selenide of the metal (U.S. Pat. No. 4,880,761).
While the syntheses of oxide zeolites and their sulfide and selenide analogues are well known, the capability of rationally designing the shape, size, and function of the pores of zeolites or microporous materials is lacking. In particular, the method for zeolite synthesis requires the mixing of an alkali metal hydroxide with aqueous solutions of silicate and aluminate anions to form a hydrated aluminosilicate gel of complex composition. Zeolitic solids are obtained by the subsequent heating of the gel (up to 200.degree. C.) under water vapor pressure conditions in a closed vessel. The complexity of the gel precludes any possibility of controlling the structural organization of the zeolitic solid. Thus, zeolite synthesis has remained as much an art as a science (See A. Dyer, "An Introduction to Zeolite Molecular Sieves" John Wiley and Sons, New York (1988); R. M. Barrer, "Hydrothermal Chemistry of Zeolites" Academic Press, New York (1982); J. M. Newsam, "The Zeolite Cage Structure", Science, 231:1093 (1986)).
An extensive amount of work has been done on the synthesis of metal-organic solids, though none of the resulting materials possess microporous properties comparable to those obtained through the use of this invention.
For example, Toshitake Iwamoto, "Inclusion Compounds of Multi-Dimensional Cyanometal Complex Hosts" Inclusion Compounds, Vol. 5 (Eds.: J. L. Atwood, J. E. D. Davies, D. D. Macnicol), Oxford University Press (1991 ) p. 177, and references therein, provides a review on the Hoffmann-type compounds and their derivatives, where 1D, 2D and 3D frameworks are produced by linking one metal atom M to another M' to form M--CN--M' type solids. Other reports are B. F. Hoskins and R. Robson, "Design and Construction of a New Class of Scaffolding-Like Materials Comprising Infinite Polymeric Frameworks of 3D-Linked Molecular Rods. A Reappraisal of the Zn(CN).sub.2 and Cd(CN).sub.2 Structures and the Synthesis and Structure of the Diamond-Related Frameworks [N(CH.sub.3).sub.4 ][Cu.sup.I Zn.sup.II (CN).sub.4 ] and Cu.sup.I [4,4',4",4'"-tetracyanotetraphenylmethane]-BF.sub.4.xC.sub.6 H.sub.5 NO.sub.2," J. Am. Chem. Soc., 112:1546 (1990); B. F. Hoskins and R. Robson, "Infinite Polymeric Frameworks Consisting of Three-Dimensionally Linked Rod-Like Segments," J. Am. Chem. Soc. 111:5962 (1989); S. R. Batten, B. F. Hoskins, and R. Robson, "3D Knitting Patterns. Two Independent, Interpenetrating Rutile-Related Infinite Frameworks in the Structure of Zn[C(CN).sub.3 ].sub.2," J. Chem. Soc., Chem. Commun. 445 (1991); B. F. Abrahams, B. F. Hoskins, D. M. Michall, and R. Robson, "Assembly of Porphyrin Building Blocks into Network Structures with Large Channels," Nature 369:727 (1994); G. B. Gardner, D. Venkataraman, J. S. Moore, and S. Lee, "Spontaneous Assembly of a Hinged Coordination Network," Nature 374:792 (1995); 0. M. Yaghi, G. Li, and T. L. Groy, "Preparation of Single Crystals of Coordination Solids in Silica Gels: Synthesis and Structure of Cu.sup.II (1,4-C.sub.4 H.sub.4 N.sub.2) (C.sub.4 O.sub.4)(OH.sub.2).sub.4," J. Solid State Chem., 256 (1995). O. M. Yaghi and G. Li, "Presence of Mutually Interpenetrating Sheets and Channels in the Extended Structure of Cu(4,4'-bipyridine)Cl," Angew. Chem., Int. Ed. Engl., 207 (1995).
All metal-organic solids prepared to date are either (a) one dimensional (1D), two dimensional (2D), or three dimensional (3D) dense solids having no porosity or (b) solids that are made by the formation of linkages between the metal, M, and a bifunctional, trifunctional, or tetrafunctional organic ligand, L, containing monodentate functional groups, around a ternplating agent, T. One possible structure, having a diamond-like framework, is shown as an example of the effect of the templating agent (Formula 1 ).
Formula 1 below represents a schematic illustration of the assembly of a metal-organic framework in the presence of a templating agent, T. Here a fragment of a solid is shown with the small spheres representing a metal ion, M, capable of binding to four ligands in a tetrahedral geometry, while the dark rod represents a bifunctional organic ligand, L, capable of binding metal ions at its ends and encapsulating the templating agent within a pore. ##STR1##
Metal-organic solids may assume other framework types, depending on the preferred coordination geometry of the metal ion and the organic ligand.
Microporosity in the aforementioned metal-organic solids has not been demonstrated due to at least two problems. First, the ternplating agent interacts strongly with the metal-organic framework, thus making it impossible to remove the templating agent from the solid without altering or destroying the framework. In that way, the ability of the solid to adsorb another molecule, or readsorb the templating agent to yield the original material, is lost. So, it is desirable to keep the templating agent-framework interactions to a minimum while maximizing the strength of intra-framework bonding between the organic ligand and the metal ion. Secondly, for many metal-organic solids the pores are not occupied by templating agents, but with interpenetrated frameworks. Formula 2 below shows an example where one framework has interpenetrated another identical framework. Extensive framework interpenetration can cause the porous space of a single framework to be filled, resulting in a dense solid that will not adsorb molecules or ions. In Formula 2 below, two interpenetrated diamond-like frameworks (distinguished with light and dark shades) are shown. Each framework standing alone forms a porous structure. However, interpenetration in this case fills those pores. ##STR2##
For a given solid, as the number of interpenetrating frameworks increases, the material becomes more densly packed, and thus, the channels and pores present in the material become smaller, perhaps to the extent that the material loses porosity to even the smallest adsorbing species. Attempts to rationally design microporous materials have resulted in nonporous solids due to interpenetration (see O. Ermer and L. Lindenberg, "Double-Diamond Inclusion Compounds of 2,6-Dimethylideneadamantane- 1,3,5,7-tetracarboxylic Acid" Helv. Chim. Acta 74:825 ( 1991 ); O. Ermer, "Five-Fold Diamond Structure of Adamantane-1,3,5,7-tetracarboxylic Acid" J. Am. Chem. Soc. 110:3747 (1988); S. R. Batten, B. F. Hoskins, and R. Robson, "3D Knitting Patterns. Two Independent, Interpenetrating Rutile-Related Infinite Frameworks in the Structure of Zn[C(CN).sub.3 ].sub.2," J. Chem. Soc., Chem. Commun. 445 (1991)).
Therefore, this invention details the first successful rational synthetic approach to the formation of crystalline metal-organic solids that show effective microporous activity, having (a) structural integrity preserved in the absence of a templating agent and (b) no or minimal amounts of interpenetrating frameworks so that channels and pores that can accomodate transfer and binding of molecules or ions exist within the solid. Given the great impact of zeolitic materials on the global economy, it would be a significant improvement in the art if a method existed for rationally designing crystalline microporous materials.
The method of this invention provides to the art such a process. By the use of the subject invention, crystalline microporous materials can be prepared which have controlled pore distributions and sizes, and which are useful in a variety of industries.
These materials form by the solution reaction of a metal ion selected from the group consisting of: Mg, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Hg, A1, Ga, In, T1, Si, Ge, Sn, Pb, As, Sb, and Bi, with a ligand having multidentate functional groups, and a templating agent.
It is believed that the invention of the present application provides to the art a novel method for the preparation of microporous materials which are useful in industries such as catalysis, gas purification, ion-exchange, the removal of impurities from industrial aqueous streams, the removal of impurities from hydrocarbon streams, the removal of color from paper mill waste waters, the removal of metals from aqueous solutions, the removal of metals from hydrocarbon solutions, the removal of hydrocarbon contaminants from aqueous systems, the removal of hydrocarbon contaminants from hydrocarbon systems, filtration, and seperation materials, and the like.
It is accordingly an object of this invention to provide to the art a method for the preparation of novel microporous materials. It is a still further object of this invention to provide to the art a method for the preparation of novel microporous materials in a simple straightforward manner which method would allow control over the resultant final product.
It would be a further improvement in the art if the synthesis of microporous materials could be performed under room temperature or mild reaction conditions (relative to those used to synthesize oxide microporous materials). It would be a still further improvement in the art if the microporous materials could be prepared from simple metal salts and organic ligands. It would be an even further improvement in the art if the aforementioned synthetic method could result in the formation of crystalline microporous materials, having no pore or channel inhomogeneity.
Further objects of this invention will appear hereinafter.